Composition of Blood

Formed ElementsFormed Elements

1.1. Erythrocytes.Erythrocytes.

2.2. Leukocytes.Leukocytes.

3.3. Platelets.Platelets. Plasma.Plasma.

Plasma

Straw-colored liquid.Straw-colored liquid. Consists of HConsists of H220 and dissolved solutes.0 and dissolved solutes.

Ions, metabolites, hormones, antibodies.Ions, metabolites, hormones, antibodies. NaNa++ is the major solute of the plasma. is the major solute of the plasma.

Plasma Proteins

Constitute 7-9% of plasma.Constitute 7-9% of plasma. Provide the colloid osmotic pressure Provide the colloid osmotic pressure

needed to draw Hneeded to draw H220 from interstitial fluid 0 from interstitial fluid

to capillaries.to capillaries. Maintain blood pressure.Maintain blood pressure.

Albumin: Albumin: Accounts for 60-80% of plasma Accounts for 60-80% of plasma

proteins.proteins.

Plasma Proteins

Globulins:Globulins: globulin:globulin:

Transport lipids and fat soluble vitamins.Transport lipids and fat soluble vitamins. globulin: globulin:

Transport lipids and fat soluble vitamins.Transport lipids and fat soluble vitamins. globulin: globulin:

Antibodies that function in immunity.Antibodies that function in immunity.

Plasma Proteins

Fibrinogen:Fibrinogen: Constitutes 4% of plasma proteins.Constitutes 4% of plasma proteins. Important clotting factor.Important clotting factor. Converted into fibrin during the clotting Converted into fibrin during the clotting

process.process.

Formed Elements of Blood

Include 2 types of blood cells:Include 2 types of blood cells: RBCs (red blood cells):RBCs (red blood cells):

Most numerous of the two.Most numerous of the two. WBCs (white blood cells).WBCs (white blood cells).

PlateletsPlatelets

Diagram showing formed elements

Erythrocytes(RBC)

Flattened biconcave discs.Flattened biconcave discs. Provides increased surface area through Provides increased surface area through

which gas can diffuse.which gas can diffuse. Lack nuclei and mitochondria.Lack nuclei and mitochondria. Live for approximately 120 daysLive for approximately 120 days Contain 280 million hemoglobin with 4 Contain 280 million hemoglobin with 4

heme chains (contain iron).heme chains (contain iron).

Leukocytes

Contain nuclei and mitochondria.Contain nuclei and mitochondria. Move in amoeboid fashion.Move in amoeboid fashion.

Can squeeze through capillary walls Can squeeze through capillary walls (diapedesis).(diapedesis).

Almost invisible, so named after stains.Almost invisible, so named after stains. Neutrophils are the most abundant WBC.Neutrophils are the most abundant WBC.

Accounts for 50 – 70% of WBCs.Accounts for 50 – 70% of WBCs. Involved in immune function.Involved in immune function.

Platelets

Also called thrombocytes.Also called thrombocytes. Smallest of formed elements.Smallest of formed elements.

Are fragments of megakaryocytes.Are fragments of megakaryocytes. Lack nuclei.Lack nuclei.

Have amoeboid movement.Have amoeboid movement. Important in blood clotting:Important in blood clotting: Constitute most of the mass of the clot.Constitute most of the mass of the clot.

Release serotonin to reduce blood flow to area.Release serotonin to reduce blood flow to area. Secrete growth factorsSecrete growth factors

Maintain the integrity of blood vessel wall.Maintain the integrity of blood vessel wall.

Function of Platelets

Platelets normally repelled away from Platelets normally repelled away from endothelial lining by prostacyclin endothelial lining by prostacyclin (prostaglandin).(prostaglandin).

Do not want to clot normal vessels.Do not want to clot normal vessels.

Circulation of blood The human circulatory system is really a two-The human circulatory system is really a two-

part system whose purpose is to bring oxygen-part system whose purpose is to bring oxygen-bearing blood to all the tissues of the body. bearing blood to all the tissues of the body. When the heart contracts it pushes the blood out When the heart contracts it pushes the blood out into two major cycle: into two major cycle:

1.Pulmonary cycle. 1.Pulmonary cycle.

2.Systemic cycle 2.Systemic cycle

Systemic cycle In the In the systemic loopsystemic loop, the blood circulates into , the blood circulates into

the body’s systems, bringing oxygen to all its the body’s systems, bringing oxygen to all its organs, structures and tissues and collecting organs, structures and tissues and collecting carbon dioxide waste. carbon dioxide waste.

The systemic cycle is controlled by the left The systemic cycle is controlled by the left

side of the heartside of the heart

The systemic loop begins when the oxygen-rich The systemic loop begins when the oxygen-rich blood coming from the lungs enters the upper blood coming from the lungs enters the upper left chamber of the heart, the left atriumleft chamber of the heart, the left atrium

As the chamber fills, it presses open the As the chamber fills, it presses open the mitral mitral valvevalve and the blood flows down into the left and the blood flows down into the left ventricle. ventricle.

When the ventricles contract during a heartbeat, When the ventricles contract during a heartbeat, the blood on the left side is forced into the the blood on the left side is forced into the aortaaorta..

The blood leaving the aorta brings oxygen to all The blood leaving the aorta brings oxygen to all the body’s cells through the network of ever the body’s cells through the network of ever smaller arteries and capillaries. smaller arteries and capillaries.

The used blood from the body returns to the The used blood from the body returns to the heart through the network of veins. heart through the network of veins.

All of the blood from the body is eventually All of the blood from the body is eventually collected into the two largest veins: collected into the two largest veins:

i) the i) the superior vena cavasuperior vena cava, which receives blood , which receives blood from the upper body. from the upper body.

ii) the ii) the inferior vena cavainferior vena cava, which receives blood , which receives blood from the lower body region. from the lower body region.

Both venae cavae empty the blood into the Both venae cavae empty the blood into the right atrium of the heart. right atrium of the heart.

Systemic arteries contains oxygen rich blood Systemic arteries contains oxygen rich blood and appears bright red.and appears bright red.

Systemic veins contains oxygen poor blood Systemic veins contains oxygen poor blood and appears dark maroon. and appears dark maroon.

Diagram showing systemic circulation of blood

Pulmonary cycle In the In the pulmonary looppulmonary loop, the blood circulates to , the blood circulates to

and from the lungs, to release the carbon dioxide and from the lungs, to release the carbon dioxide and pick up new oxygen. and pick up new oxygen.

The pulmonary cycle is controlled by the right The pulmonary cycle is controlled by the right side of the heart.side of the heart.

Blood collected in right atrium passes into right Blood collected in right atrium passes into right ventricle through the ventricle through the tricuspid valvetricuspid valve. When the . When the ventricle contracts, the blood is pushed into the ventricle contracts, the blood is pushed into the pulmonary arteries. pulmonary arteries.

Pulmonary arteries divide into arterioles of the Pulmonary arteries divide into arterioles of the lungs. lungs.

These arterioles take blood to the pulmonary These arterioles take blood to the pulmonary capillaries where carbon dioxide and oxygen is capillaries where carbon dioxide and oxygen is exchanged. exchanged.

The blood then enters the pulmonary venules and The blood then enters the pulmonary venules and flows through the pulmonary veins back to the flows through the pulmonary veins back to the left atrium.left atrium.

Pulmonary artries contain oxygen poor blood.Pulmonary artries contain oxygen poor blood. Pulmonary veins contain oxygen rich blood.Pulmonary veins contain oxygen rich blood.

Diagram showing pulmonary cycle